Occupational studies are conducted to identify and quantify chemical and other causes of cancer and to understand mechanisms of carcinogenesis. Etiologic investigations utilize sophisticated industrial hygiene methods to assess occupational exposures and biochemical components to elucidate mechanisms of carcinogenic action and individual susceptibility. Methodologic studies are designed to improve study techniques and to provide direction for future research. Major etiologic investigations focus on working populations exposed to benzene, other organic solvents, acrylonitrile, formaldehyde, diesel exhausts, combustion products, electromagnetic fields, pesticides, and silica. Findings linking cancer with occupational exposures included an excess of respiratory cancers among butchers in Sweden; leukemia among Chinese workers exposed to benzene and other solvents; laryngeal cancer among workers in several dusty occupations in Turkey; leukemia among workers in agriculture, healthcare, and occupational with possible solvent exposure; occupational exposure to solvents, K-ras mutations and pancreatic cancer; gastric adenocarcinoma and woodworking occupational; farming and risk of multiple myeloma; truck drivers and risk of lung cancer; and cancers of the esophagus, lung and ovary among dry cleaners. Ongoing projects to evaluate occupational exposures include case-control studies of bladder cancer in Spain and New England, lung cancer in Russia, renal cancer in Eastern Europe, mesothelioma in the United States, and non-Hodgkin's lymphoma in the U.S. Cohort studies of occupational groups include miners with exposure to diesel exhausts, farmers with exposure to pesticides and other agricultural chemicals, women in many occupations in Shanghai, Coast Guard marine inspectors exposed to solvents, shipyard workers exposed to asbestos, paints and welding fumes, and cohorts of industrial workers with exposure to benzene, acrylonitrile, formaldehyde, and solvents.